Tarih ve Takvim
15
Multi-Calendar Converter: Gregorian, Hijri, Julian & Unix Epoch
Convert dates across historical, religious, and computing systems. Gregorian, Hijri, Julian, Hebrew, Persian, Maya, Julian Day (JD), Unix Timestamp, and ISO 8601.
Çoklu Takvim ve Tarih Dönüştürücü
Jülyen Günü (JD) köprüsü üzerinden dünya takvimleri, antik sistemler ve zaman damgaları arasında çift yönlü hassas dönüşüm.
Miladi1 Ocak 2026
Hicri12 Recep 1447
Hafta GünüPerşembe
Jülyen Günü (JD)2461041.50
Popüler
Teknik & Zaman
Tarihsel
Miladi Takvim (Gregorian)
Normal YılPerşembe
Uluslararası standart güneş takvimi.
:
2026-01-01 00:00:00
Hicri Takvim (Islamic / Kameri)
Artık Yıl (355g)al-khamis
1 Muharrem 1 H (16 Temmuz 622) başlangıçlı saf ay takvimi.
12 Recep 1447 H
Jülyen Takvimi (Eski Usul / Rumi Kök)
Normal YılM.Ö. 46 Julius Caesar reformu (her 4 yılda bir artık yıl).
19 Aralık 2025 (Jülyen)
Celali / İran Takvimi (Şemsi Hicri)
Artık YılPanjshanbeh
Ömer Hayyam kökenli, 2820 yıllık döngüye sahip hassas güneş takvimi.
12 Dey 1404 (Şemsi)
İbrani Takvimi (Hebrew / Yahudi)
12 Aylık Normal Yıl354 Gün
M.Ö. 3761 başlangıçlı, 19 yıllık Meton döngüsüne sahip luni-solar takvim.
12 Teveth 5786
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Multi-Calendar Converter Guide: Converting Between Historical, Solar, Lunar, and Computing Date Systems
Throughout civilization, societies have measured time using different celestial anchors—the solar cycle of the seasons, the monthly phases of the Moon, or religious and mythological milestones. While the Gregorian calendar is the international civil standard today, historical scholarship relies on the Julian calendar, religious observances follow the Islamic (Hijri) and Hebrew calendars, astronomy uses continuous Julian Dates (JD), and software infrastructure runs on Unix timestamps.
The HesapYap Multi-Calendar Converter anchors all date formats to a single continuous astronomical timeline, allowing bi-directional conversion across civil, historical, lunar, lunisolar, and computational systems.
1. Solar Civil Calendars
The Gregorian Calendar
Promulgated by Pope Gregory XIII in October 1582 via the papal bull Inter gravissimas, this system corrected a centuries-old drift in the Julian calendar that was causing the spring equinox (and Easter) to drift earlier in the year.
A mean tropical year lasts approximately 365.2422 solar days. The Gregorian calendar matches this duration by refining the leap year formula:
- Every year evenly divisible by 4 is a leap year (366 days).
- Century exception: Years divisible by 100 are not leap years, unless they are also evenly divisible by 400. (Thus, 1600 and 2000 were leap years, while 1700, 1800, and 1900 were ordinary 365-day years).
The Gregorian calendar yields an average year length of 365.2425 days, losing only about one day every 3,200 years. Adoption varied widely across regions: Catholic Europe adopted it in 1582, Great Britain and its colonies in 1752, Russia in 1918, and Turkey for official civil use on January 1, 1926.
The Julian Calendar
Introduced by Julius Caesar in 46 BCE with the assistance of the Alexandrian astronomer Sosigenes, the Julian calendar streamlined the Roman year to a flat 365 days, adding a leap day every four years without century exceptions (average length: 365.25 days).
This 11-minute-per-year error accumulated to a 10-day discrepancy by 1582, and stands at 13 days today. Historians comparing documents from the 16th to 20th centuries must account for whether records were logged in the "Old Style" (Julian) or "New Style" (Gregorian) format.
2. Lunar and Lunisolar Traditions
The Islamic (Hijri) Calendar
The Hijri calendar is a purely lunar system consisting of 12 lunar months in a year of 354 or 355 days. Its epoch begins with the Hijrah—the migration of the Prophet Muhammad from Mecca to Medina in 622 CE.
- Because a lunar year is roughly 10 to 11 days shorter than a solar tropical year, Hijri dates advance through all four solar seasons over a cycle of roughly 33 solar years.
- Our calculator uses the standard arithmetical (tabular) algorithm. However, official religious observances (such as the start of Ramadan or Eid) depend on local crescent moon sightings (ru'yat al-hilal) and can vary by ±1 day depending on geographical location and administrative declarations.
The Persian (Solar Hijri / Jalali) Calendar
Rooted in the 11th-century astronomical reforms led by Omar Khayyam, the Persian calendar is a strictly solar system. While its epoch is also the Hijrah, its new year begins on the exact astronomical moment of the northward equinox (Nowruz, around March 20–21).
- The first 6 months have 31 days, the next 5 have 30 days, and the final month has 29 days (30 in leap years).
- Its leap-year cycle is tied directly to actual equinox observations rather than simple mathematical approximations, making it more accurate relative to the solar year than the Gregorian calendar.
The Hebrew Calendar
A lunisolar system that balances monthly lunar phases with the annual solar cycle:
- Months alternate between 29 and 30 days to follow the Moon.
- To prevent seasonal drift so agricultural festivals remain in their correct seasons, an extra 30-day leap month (Adar II) is inserted 7 times within every 19-year Metonic cycle.
3. Mesoamerican Cycles: The Maya Calendar
The Maya civilization tracked time through three distinct, intertwined systems:
- The Long Count: A linear tally of elapsed days from a mythological base date (August 11, 3114 BCE in the standard GMT correlation). Recorded hierarchically as
baktun.katun.tun.uinal.kin:
- 1 kin = 1 day
- 1 uinal = 20 days
- 1 tun = 360 days (18 uinals)
- 1 katun = 7,200 days (20 tuns)
- 1 baktun = 144,000 days (~394.3 tropical years)
- Haab: A 365-day solar civil cycle made of 18 named months of 20 days each, followed by a 5-day unlucky period (Wayeb).
- Tzolk'in: A 260-day sacred almanac created by the permutation of 20 day signs with the numbers 1 through 13.
4. Scientific and Astronomical Timekeeping
Julian Day (JD)
Developed by Joseph Scaliger in 1583, the Julian Day system discards calendar months, years, and leap years entirely. It is simply a continuous count of elapsed days and fractions of a day since noon (12:00 UTC) on January 1, 4713 BCE (in the proleptic Julian calendar).
Astronomers rely on JD because calculating the exact interval between two celestial events requires nothing more than subtracting one Julian Day number from another. Setting the day boundary at noon ensures that nighttime observations made across midnight do not fall into two different calendar days.
Modified Julian Date (MJD)=JD−2,400,000.5
(MJD resets the day boundary to midnight 00:00 UTC and truncates the large initial digits, making it convenient for satellite tracking and geodesy).
5. Computing and Digital Standards
Unix Timestamp (POSIX / Epoch Time)
Modern operating systems, network protocols, databases, and APIs represent time as the total number of seconds elapsed since midnight UTC on January 1, 1970 (excluding leap seconds).
- The Year 2038 Problem (Y2038): Legacy 32-bit signed integer implementations reach their maximum capacity at
2,147,483,647seconds on January 19, 2038, at 03:14:07 UTC. At that instant, unpatched counters will overflow into negative numbers, interpreting the date as December 13, 1901. Modern systems mitigate this by transitioning to 64-bit integer timestamps, which remain stable for over 290 billion years.
Microsoft Excel Serial Dates (The 1900 Leap Year Bug)
Excel represents dates as sequential numbers where day 1 equals January 1, 1900. To preserve backward compatibility with Lotus 1-2-3, Excel intentionally replicates a historical bug: it treats 1900 as a leap year, assuming February 29, 1900 existed when it did not. Consequently, all serial numbers after February 28, 1900 are offset by one day.
(Legacy versions of Excel for Macintosh historically used a 1904 base date, introducing a roughly 4-year-and-1-day variance when moving spreadsheets between older environments).
ISO 8601 International Standard
- Calendar Date:
YYYY-MM-DD(e.g.,2026-10-25)
- Week Date:
YYYY-Www-D(e.g.,2026-W43-7). Under ISO rules, Monday is day 1 of the week, and Week 01 of any year is defined as the week containing the first Thursday of that year.
6. Comparison of Major Systems
Calendar / System | Core Basis | Average Year Length | Epoch / Origin |
|---|---|---|---|
Gregorian | Solar (Tropical) | 365.2425 days | Traditional birth of Jesus Christ |
Julian | Solar (Fixed 4-year leap) | 365.25 days | Julian reform (46 BCE) |
Islamic (Hijri) | Pure Lunar (12 lunations) | 354.36 days | Hijrah (622 CE) |
Persian (Solar Hijri) | Solar (Astronomical Equinox) | 365.2422 days | Hijrah / Vernal Equinox (Nowruz) |
Hebrew | Lunisolar (Metonic cycle) | Variable (353–385 days) | Traditional Creation (3761 BCE) |
Julian Day (JD) | Continuous elapsed days | — | Jan 1, 4713 BCE at 12:00 UTC |
Unix Epoch | Continuous elapsed seconds | — | Jan 1, 1970 at 00:00:00 UTC |
How to Use the Calendar Converter
- Select an Input Format: Enter a standard Gregorian date, a Hijri year, a raw Unix timestamp, or an Excel serial number.
- Specify Time and Timezone: Ensure fractional day precision for astronomical calculations (JD/MJD) and UTC-to-local Unix mapping.
- Instant Cross-Conversion: View real-time conversions across Gregorian, Julian, Islamic, Hebrew, Persian, Maya, ISO week, and Unix systems side-by-side.
References and Scientific Standards
- Jean Meeus, Astronomical Algorithms (Second Edition, Willmann-Bell).
- P. Kenneth Seidelmann (ed.), Explanatory Supplement to the Astronomical Almanac.
Disclaimer: Conversions are computed using recognized mathematical, astronomical, and arithmetical algorithms for research, software development, and educational purposes. Historical transitions to the Gregorian calendar occurred at varying local dates, and religious lunar calendars may vary by ±1 day based on actual astronomical crescent sightings.